I think this is just another example of lack of common knowledge. Something isn't common knowledge unless everyone knows it and everyone also knows that everyon

I think this is just another example of lack of common knowledge. Something isn't common knowledge unless everyone knows it and everyone also knows that everyone knows it. "Have you tried X"? No shit, X is the first thing that I tried." is classic lack of common knowledge. You thought trying X being the first thing was common knowledge, but it wasn't, so your "advisor" suggested it. You both knew X is the first thing to try, but he didn't know for sure that you knew that, so he started there. And now you're imagining they think you're an idiot, and it's not in common knowledge that you're an idiot (probably because it's not true), so it rankles. As an advisor I would start this exchange with: "Ok, so I assume you've tried all the normal things like X?" Literally saying you're assuming something both puts the thing in common knowledge and acknowledges that it wasn't before, even though you probably both individually know the thing. "Yes, of course." "Ok, what about..." -- much smoother! "Actually, no! Of course X, now that you say it!" "Great!" -- also much smoother!